Elaine writes:
Bifidis is normally the only gut bacteria present in breast fed babies. Early researchers felt that when bifidis persists into early childhood and beyond, it correlated with celiac disease. I, personally, do not believe in using bifidis in a probiotic or in a yogurt culture.

The use of different strains of probiotics has been a subject of much discussion. I do not pretend to know the answers for most of them and have told the list that spending one year doing library research convinced me that there is more ambiguity than black and white answers.

To further the confusion, very smart people are advising some very dumb things. Companies have jumped on the band wagon proposing oral administration of various types of Lactobacillus strains along with things like bifidis and have given absolutely no attention to the fact that these bacteria will mutate depending upon what is in the colon for them "to eat."

Seth on healing crow referenced a wonderful article which was a chapter in a book written by his former professor of bacteriology at the University of Wisconsin. (copyright 2000 Kenneth Todar. Bacteriology pg 303. I have it in front of me.

"The normal flora of humans is exceedingly complex and consists of more than 200 species of bacteria. The makeup of the normal flora depends upon various factors including genetics, age, sex, stress, nutrition and diet of the individual......The distribution of the bacterial flora of humans is shown in the flg table. This table lists only a fraction of the total bacterial species that occur as normal flora of humans and does not express the total number or concentration of bacteria at any site."

It then goes on to list many species including Bacteroides sp and Bifidobacterium bifidum. I understand that these two are closely related. Others include Enterobacteriaceae (E. coli) and Lactobacillus, etc.

Then comes the confusing part:
"The greatest number of bacteria are found in the lower intestinal tract, specifically the colon and the most prevalent bacteria are the Bacteroides, a group of Gram-negative, anaerobic, non-sporeforming bacteria. They have been implicated in the initiation of colitis and colon cancer.
Bifidobacterium bifidum is the Gram-positive counterpart to the Bacteroides in the colon. They are anaerobic, non-sporeforming, lactic acid bacteria. They are the "friendly" bacteria in the intestine. Bacteroides predominate in the intestine of meat-eaters, bifidobacteria and other lactic acid bacteria predominate in the intestine of vegetarians."

From Elaine:
That said, it appears that bifidis could replace bacteroides and the implication of the latter in initiating cancer and colitis could be overcome. However, that is not certain and considering that our paleolithic diet was high in meat, I would doubt if meat is the real suspicious element in the diet. The research has indicated to me that any work done to support this thesis was not done without many other variables in the diet including high starch.
Seth provides the following information:

"Intestinal Floras of Populations That Have a High Risk
of Colon Cancer

The study finds that populations with the highest colon cancer risk have a
higher number of bifido bacteria than
populations with the lowest risk. The authors were very surprised at this
result since bifido bacteria is a "good" bacteria. Of course this is an
epidemiology study (which always have flaws) but combined with Elaine's
knowledge on the subject sends a powerful warning in my mind.

t writes:
In the case of bifidus, it has a tendency to overgrow. Each type of bacteria has different properties, different byproducts... I usually think of it in terms of different levels of tenacity and agression. Your gut is truly a multicultural society - some member are more altuistic, and others are criminal. Some are interested in improving the neighbourhood, and some are only out for themselves.

L. Acidophilus is about as community-minded a bacterial strain as you will find, with S.Thermophilus and L.Bulgaricus running a close second. The others are either less friendly, or are unknown quantities. It gets even more complicated if you consider soil based strains.

So we stick with Acidophilus in our supplements, and Acidophilus, Thermophilus and Bulgaricus in our yogurt, because they are good neighbours.

Julie writes:
I am one who had used yogurt containing Bifidus as my starter the first eight
months on the diet and after a few back to back flares where nothing helped,
Lucy clued me in that the Bifidus may have overgrown in my colon and there
for caused my endless flare. Sure enough, after I switched to the powdered
yogourmet starter I literally came out of the flare overnight! I am a big
proponent of using the powdered starters for making yogurt. Not everyone has
trouble but why risk it?